2,2',2"-Nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2 '-diyl) phosphite] is a compound having the formula I ##STR1##
This compound of formula I is useful as a processing stabilizer for organic polymers as taught in U.S. Pat. Nos. 4,318,845 and 4,374,219. It has been found that the compound can exist in a number of crystalline forms as well as an amorphous form. These forms of the compound of formula I are described in U.S. Pat. Nos. 5,276,076; 5,326,802; 5,331,031; 5,334,739; 5,344,860 and 5,373,040. These different forms of the compound of formula I exhibit acceptable properties in respect to handling, apparent density, flowability, meterability, storage stability, hydrolytic stability and better migration into polymeric substrates.
The beta, triclinic crystalline form is specifically described in U.S. Pat. Nos. 5,326,802 and 5,344,860. These patents describe the process of making the beta form by solvent crystallization or by melt crystallization. Both prior art processes require solvents or high temperature in addition to an extended crystallization time. The present invention pertains to a process for a solvent-free and time saving crystallization leading to the instant beta, triclinic form of the compound of formula I.